1. Field of the Invention
The present invention relates to a programmable element and a manufacturing method of a semiconductor device including the programmable element, particularly to a programmable element used in a programmable logic device such as a field programmable gate array (hereinafter, referred to as FPGA) and a manufacturing method of a semiconductor device including the programmable element.
2. Description of the Related Art
A programmable logic device such as an FPGA is a semiconductor device including multiple logic circuitries and programmable elements formed on interconnections between the multiple logic circuitries. The programmable logic device exerts a predetermined function with predetermined ones of the multiple logic circuitries connected to or disconnected from each other through an appropriate control of the programmable elements.
In a conventional programmable logic device, antifuses, erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs) or static random access memories (SRAMs) are employed as the programmable elements with which desired logic circuitries are made connected to or disconnected from one another.
However, a semiconductor device including antifuses as programmable elements (refer to Japanese Patent Application Publication No. 2003-115537 (FIG. 3)) has a problem that a program therein cannot be rewritten. Meanwhile, a semiconductor device including EPROMs or EEPROMs as programmable elements has a problem that withstand voltages of elements and the like in the semiconductor device need to be increased, since these programmable elements require a high program voltage, that is, a high voltage needs to be applied to these programmable elements when the semiconductor device is programmed. Moreover, a semiconductor device including SRAMs as programmable elements has a problem that a program written therein is erased once the semiconductor device is powered off.
Thus, it is currently difficult to provide such a program element with good program characteristics that: a program can be re-written; the program voltage is low; and the program is retained after powering-off.